A physically unclonable function (PUF) technology is a novel method for protecting the data of a semiconductor chip. That is, the use of the PUF technology can prevent the data of the semiconductor chip from being stolen. In accordance with the PUF technology, the semiconductor chip is capable of providing a random code. This random code is used as a unique identity code (ID code) of the semiconductor chip to achieve the protecting function.
Generally, the PUF technology acquires the random code of the semiconductor chip according to the manufacturing variation of the semiconductor chip. This manufacturing variation includes semiconductor process variation. That is, even if the PUF semiconductor chip is produced by a precise fabricating process, the random code cannot be duplicated. Consequently, the PUF semiconductor chip is suitably used in the applications with high security requirements.